Switching elements for communication networks generally include multiple input ports for receiving data from a plurality of different sources and multiple output ports for transmitting the received data to various destinations over the network. An example of a known switching element includes an integrated circuit device having an input for receiving data from a communication network, and an input buffer, which may include a number of queues for temporarily storing data before being output from the device onto the network. The device further includes a scheduler for controlling the order in which data stored in the various queues is output from the device, according to a set of predetermined priority rules.
The speed at which data can be transferred between any two points in a network is determined by the components of the network path, for example, communication links and switching elements, each of which has an associated delay. In an optical communication system, switching elements potentially contribute to a relatively high proportion of the total delay associated with a communication path due to the conversion of optical signals to electrical signals and vice versa and delays associated with the transfer of data from an input port of the switching element to the appropriate output port. Therefore, one of challenges facing designers is to minimize the time for transferring data cells across a switching element. Ideally, the capacity for data transfer between an input port and an output port of a switching element should at least match the capacity of the communication links to which the ports are connected.